Double-step lamination of grain-oriented Y-Ba-Cu-O superconducting ceramics

The uniformity of grain alignment and anisotropic superconducting properties were investigated in laminated tape-cast YBa₂Cu₃O_7-x ceramics. Large, platey YBa₂Cu₃O_7-x grains were prepared by gentle grinding of pellets prepared by liquid-phase sintering. A mixture of pre-reacted BaCuO₂ and CuO was added as a molten flux. The grain-oriented specimens were then prepared by tape-casting followed by lamination and sintering. A high degree of grain orientation was observed near the surface of the specimen. Successive polishing and X-ray diffraction studies revealed that the effective depth of the oriented layer was approximately 200 μm. The small anisotropy observed in the critical current density calculated from the magnetization provided additional evidence for the non-uniformity of the grain alignment across the sample. By reducing the thickness of the laminated sample to the effective depth for obtaining a uniform structure, polycrystalline ceramic samples with a homogeneous and high degree of grain orientation were obtained by a double lamination method.